DBMS_METADATA.GET_DDL works for every other objects of U1 (tables, views, ... for example) except for dblinks.

DBMS_METADATA.GET_DDL works for every objects of U2, includes DBL2.What can cause this behavior?

I tried to add "select catalog role" to U1, even when I know that I need it only for objects from other users.I tried to create DBL2 in U1 - same results.I tried to re-create dblink using full connection string - with same result.